A full-scale wind tunnel test was conducted in the 40- by 80-Foot Wind Tunnel at NASA Ames Research Center to evaluate the effects of individual blade control on blade-vortex interaction noise. This international joint program involved NASA Ames Research Center, U.S. Army Aeroflightdynamics Directorate, ZF Luftfahrttechnik, DLR and Eurocopter Deutschland. A four-bladed BO 105 rotor system was mounted on the NASA/U.S. Army Rotor Test Apparatus, with the rotoring pitch links replaced by hydraulic actuators. These actuators generated high-frequency, low-amplitude blade pitch inputs. Individual blade pitch inputs included sinusoidal 2/rev, 3/rev and 6/rev. Additionally, multi-frequency inputs allowed for blade pitch changes at discrete azimuth locations. The Acoustic Survey Apparatus was used to acquire acoustic data with two microphones in a horizontal plane below the advancing side of the rotor. A fixed microphone recorded acoustic data aft of the rotor on the retreating side. The typical acoustic signature consisted of one strong BVI event and several smaller, secondary events. Acoustic data for the rotor without individual blade control inputs and data with inputs were compared for variations in sound pressure level.
Individual blade control effects on blade-vortex interaction noise
Die Auswirkungen einer individuellen Rotorblattregelung auf die Geräuschbildung, hervorgerufen durch die Wechselwirkung von Rotorblatt und Wirbeln
Forum, Annual Forum, American Helicopter Society, 50 ; 1 ; 81-101
1994
21 Seiten, 34 Bilder, 5 Tabellen, 17 Quellen
Conference paper
English
Rotor blade-vortex interaction noise
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